Reducing the oil/coupler ratio is known to be an effective means for improving the sharpness of images or improving the strength of membranes. However, the oil/coupler ratio can only be reduced to a limited extent because it causes a reduction in the rate of development.
Color development accelerators are added to avoid slowing the development caused by the reduction of the oil/coupler ratio. Color development accelerators known hitherto, for example, compounds described in U.S. Pat. Nos. 2,950,970, 2,515,147, 2,496,903, 3,201,242, 4,038,075 and 4,119,462, British Patents 1,430,998 and 1,455,413, Japanese Patent Application (OPI) Nos. 15831/78, 62450/80, 62451/80, 62452/80 and 62453/80 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") and Japanese Patent Publications Nos. 12422/76 and 49728/80, have been examined. However, the effects of these compounds are not sufficient to eliminate the development retardation caused by the reduced oil/coupler ratio.